Electrical junction boxes used in telecommunications provide an organized and convenient interface for connecting telephone lines in a building, for example, with the regional lines of a telephone system. One example of such a junction box is the "building entry protection" unit or BEP. The BEP also provides a point at which the system is locally grounded.
Grounding is important for reasons of system performance and safety. An effectively grounded BEP will reduce system cross talk, or the propensity of one line to inductively pick-up and carry the undesired signals of a neighboring line, causing interference between the two lines. Grounding is also important to protect users of the telephones in the event that lightning strikes the cable carrying the linesinto the building, or a high power electrical line contacts the telephone cable. A grounded BEP will conduct the electrical current from a lightning strike or electrical line safely to ground. An ungrounded BEP will allow the current to enter the telephone system within the building, damaging equipment and presenting a lethal hazard to anyone using a telephone.
One design of a BEP has a metal housing, mounted within the building, connected to a local ground by a grounding strap or other means well known in the art. Wire connectors, for example insulation displacement connectors (IDCs) having connection terminals on opposite ends, are mounted in the housing. A cable containing the outside telephone lines attached to the terminals on one end, telephone lines from telephones within the building are attached to the terminals on the other end.
It is convenient to mount the connectors on a metal frame that is hingedly attached to the housing. The frame pivots on the hinge to allow ready access to the inner terminals enclosed within.
Surge protectors are mounted on the wire connector to protect the system. When excess current is present, for example, during a lightning strike, the surge protector grounds the affected line to the metal frame of the BEP which is, in turn, electrically connected to the metal housing which in turn electrically connected to ground. Thus the current is effectively shunted to ground without entering the telephone system within the building if the path from the outside lines through the BEP frame, through the BEP housing and lastly through the grounding strap is a continuous path offering low electrical resistance. The article cable also has a metal shield that is grounded to the BEP and ultimately connected to the ground.
Typically hinge connections between the frame and the housing provide poor electrical connections which can compromise the path to ground. The hinge elements must move easily relative to each other and cannot be tightly bound together in contact, which is generally required for a good electrical connection. When it is necessary to electrically connect parts joined by a hinge, such as a conventional "piano" type hinge, a separate grounding strap is usually connected between the two parts to ensure a good electrical connection.
Accordingly it is an object of the invention to provide an electrically conducting hinge which provides a good electrical connection between the moving parts.
It is another object of the invention to provide an electrically conducting hinge which allows the moving parts to move easily and smoothly between an open and a closed position.
It is yet another object of the invention to provide an electrically conducting hinge with sufficient strength and stiffness to hold one moving part in an open position relative to the other.
It is still another object of the invention to provide an electrically conduction hinge which eliminates the need for a separate grounding strap between the moving parts.
These and other objects will become apparent from a consideration of the following drawings and description of the invention.